International Telemetering Conference Proceedings, Volume 11 (1975)

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The International Telemetering Conference/USA (ITC/USA) is
dedicated to the promotion and stimulation of technical growth in
telemetering and its allied arts and sciences. It is the premier
annual forum and technical exhibition providing telemetry specific
short courses, technical papers from professionals and students,
and exhibits of the industry’s leading companies. ITC/USA is
sponsored by the International Foundation for Telemetering (IFT), a
non-profit corporation dedicated to serving the technical and
professional interests of the telemetering community.

This collection contains the proceedings of the eleventh
International Telemetering Conference, October 14-16, 1975. The
conference, sponsored by the International Foundation for
Telemetering, was held at the Sheraton Inn in Silver Spring,
Maryland.

An application using a multibeam adaptive array for the simultaneous communications of command control, and telemetry data from 20 Remotely Piloted Vehicles (RPV's) to a command station is investigated. It is assumed that the RPV's are on tactical mission beyond FEBA as typically shown in Figure 1, and that communication links must be established to and from each RPV in the presence of many airborne and/or surface based jammers. The RPV's are assumed to be on data collection missions out to a maximum range of 100 km and must data link the sensor information (including digitized video of 20 Mbps) back to the tactical RPV control center. The data link will be operated at C-band. Other system parameters are summarized in Figure 2.

In the design of a tactical multi-remotely piloted vehicle (RPV) data link, the RPV data rate and update rate are crucial to the multi-RPV scenario. Data rates on the order of 150 bits per second per RPV or fewer and update rates of fewer than 2 per second per RPV must be used if the RPV's are to operate successfully in a hostile jamming environment. This limit is imposed by the amount of RF spectrum that can be obtained for applying spread-spectrum to protect the data channel. Through data management all necessary RPV command and telemetry functions can be handled at these rates.

A brief explanation of the background behind development and employment of operational RPV systems will be followed by a resume of their accomplishments and shortcomings. Reconnaissance, electronic warfare and strike systems will be covered. The main portion of the paper will discuss systems under development to support specific missions or improve RPV capabilities in general. The Compass Cope high altitude RPV, multi-mission RPVs, expendable drones, and mini-PPVs will be considered as a family of vehicles desianed to support a variety of mission requirements. In addition, programs to improve capabilities for launch, recovery, controls and sensor integration will be included. The overall emphasis is on an appreciation for the purpose and direction of the Air Force RPV development program.

The continuing evolution to smaller, more reliable electronics packages has had a tremendous impact throughout industry and the world. One application that has just recently started receiving wide spread attention is Remotely Piloted vehicles (RPVS). The smaller computers, electro-optical devices, infra-red systems, etc. have brought the RPV out of its "model airplane" stage and into the military arena. RPVs offer some distinct advantages over manned aircraft, which places them in a very competitive position for accomplishment of selected missions. Cost savings promise to be significant and their comparatively small size make them attractive for operation from small naval ships. However, the Navy faces some unique problems that must be addressed before RPVs are an integral part of the Naval Forces. The most immediate and overriding problem is recovery. Not only is the recovery platform very small, but ship's movement through all three axis further complicates the problem. This paper discusses some of the possible naval applications of RPVs, and outlines the Navy's program for solving the recovery problem.

This paper describes an approach to airborne PCM data acquisition that takes advantage of the latest technological advances in the fields of both the monolithic microcircuits and hybrid packaging. The result is a low cost system that provides a combination of long sought-after features; flexibility, modular make-up, microminiature size, high reliability and low power.

The range to the spacecraft is an important parameter for determining the transfer and synchronous orbits. The ranging equipment developed for the COMSAT General TT&C earth stations uses a fixed-tone technique to determine the distance from the earth station antenna to the satellites. Specifically, the range is calculated from the round trip propagation delay, which is determined by measuring the phase shift in four coherent audio tones. This system is similar to the ranging equipment used at the INTELSAT earth stations. New integrated circuit (IC) technology has permitted individual tone transmission which was previously not available. The ranging tones are frequency modulated in both the up- and down-links in the INTELSAT system. However, in the COMSAT General system the tones are frequency modulated in the up-link and phase modulated in the down-link. Hence, new techniques are required to determine the phase shift of the earth station equipment.

Neurophysiologic experiments are becoming increasingly numerical in nature, and may result in large quantities of data which may be practicably analyzed only by computer. A non-programmable digital controller was constructed to acquire data from a variety of remote neurophysiology experiments and to store them on magnetic tape for transport to an off-line computer. The advantages of the unit's modular design are illustrated.

Many surface acoustic wave (SAW) devices are now sufficiently well-developed that they can have a significant impact on systems design. This paper reviews the properties and limitations of SAW devices which seem particularly well suited to communications. The simple bandpass filter is considered in detail as it will undoubtedly see the widest usage of all SAW devices. The application of SAW analog matched filters in phase-shift-keyed synchronization and data demodulation is also discussed. Finally, SAW resonators and oscillators are briefly considered. A number of examples are included which show how system performance can be improved through use of SAW technology.

The analog memory device is a combination of a bipolar and a MOSFET device which stores information in analog form for several hours or more with no degradation of data. The emitter base junction of a bipolar transistor is covered with an SiO₂ layer and a voltage is applied to this point. With zero volts applied, the unit acts as a bipolar transistor. Increasing the voltage at this point increases the emitter injection efficiency of the bipolar transistor, which in turn increases the current gain of the device. An SiO₂ layer with no leakage paths can retain the charge applied to it for long periods of time; thus the gain will remain at this level as long as the charge remains on the oxide layer. A large number of such devices can be fabricated on a single chip. Such devices combined with other integrated circuits can be used, for example, for automatic equalization of transmission lines, echo suppression, and correlation detection.

A real time data compression unit was designed and fabricated for the Radio Astronomv Explorer Lunar Mission Antenna Aspect Camera. The camera takes a panoramic view of spacecraft, moon, etc. of ±35 degrees by 360 degrees. This data compressor combined information reduction and redundancy reduction. The information reduction was accomplished by subsampling (used every fourth line): and the redundancy reduction was accomplished by an adaptive run-length encoder. The adaptive run-length encoder used a zero-order predictor. Two different maximum run-lengths were used with two different data formats. Selection of the operating format depended on the sampled gray level compared to a fixed threshold. Statistical data and images indicate that the redundancy reduction technique yields a compression ratio of 8:1. Thus a combined compression ratio of 32:1 was obtained on an entire panoramic view.

Particles flux intensity measurements redundancy reduction algorithms are proposed. Accuracy criteria consists in limiting of a samples relative error maximum value. The algorithms are based on prediction or interpolation operations with a variable threshold, adaptive to a changing flux intensity. A formula for computation of an adaptive threshold zero order predictor compression ratio is deduced. Computed values show good coincidence with those received by signal and algorithm computer simulation. Adapter threshold zero order predictor (AT-ZOP) and first order interpolator (AT-FOI) algorithms applied to real telemetry data reveal their high efficiency as relating to attainable compression ratios. Algorithms compression ratio comparison results in predictor advantage against interpolator and unsignificantly small predictor loss when preliminary data smoothing is applied. Compression ratios for joint application of background removal [2] and adaptive predictor algorithms are also evaluated. AT-ZOP simplicity and high efficiency allow to recommend it for use in particle flux intensity measurements redundancy reduction systems.

The vocoplexer is a system which permits a reduction in the data rate required to transmit voice signals when many such signals are multiplexed onto a common digital line. This is accomplished through the use of a coding technique which is based on the statistical properties of voice signals. The reduction in data rate that can be realized by the vocoplexer is a function of the speech quality required. Typically, for a speech quality equivalent to PCM at 8,000 samples per second and five bits per sample, a reduction in data rate to about 1/3 can be accomplished. The descriptions in this paper are based on this quality requirement. However, for a somewhat reduced quality requirement, even greater savings can be accomplished. For example, if quality equivalent to PCM at 8,000 samples per second at four bits per sample is adequate, the vocoplexer will require approximately 9,600 bits per second. For quality equivalent to delta modulation at 18,000 bits per second the vocoplexer requires approximately 6,400 bits per second per voice channel.

As the volume of aerial photographic data increases in various applications, there is increasing demand for automated data analysis. Faster and larger computer alone is not the solution. In this paper effective and computationally efficient techniques for computer processing of the aerial photographic data are presented. They include: (1) picture data compression, (2) feature exttraction using the histograms of the original and sharpened pictures, (3) sequential target and classification, (4) threshold selection, and (5) Walsh power spectrum analysis. All of these techniques may be incorporated in a fully automated data analysis system to meet certain real-time on-line system requirement.

This paper presents the results of the instrumentation used on a firing test for making inbore measurements of projectile acceleration and base pressure. The system components; including the telemetry data link, acceleration and pressure sensors; and the packaging techniques are described. The data from a test of six 105mm proof projectiles fired in an M-68 tank gun are presented and compared with independent measurements.

An algorithm for threshold compression of the processes with the sharp variations of a level is considered. In broadening the concept on an significant sample we are successful in transmitting completely almost all the samples appropriate to the phenomenon studied; at the same time the compression ratio at the quiet parts is kept at the acceptable level. The experimental results of seismogram compression are given.

A telemetry system has been designed and built which transmits digital data from a buried earth-penetrating vehicle to the surface by magnetic induction. The transmitting package is a cylinder 10 cm in diameter by 30 cm long and draws 5 watts of dc power while transmitting. Error rates of 1.16 x 10⁻⁴ have been obtained at a range of 52 meters through soil at a data rate of 50 bits/second, utilizing only the 0-50 Hz region of the electromagnetic spectrum. Projected performance of the system in high-conductivity media indicates useful ranges exceeding 50 meters in media as conductive as sea water (4 mho/meter). System improvements are discussed which should allow severalfold increases in data rate or range over the experimentally obtained values.

Unwanted resonances can make analysis of crash instrumentation extremely difficult. These resonances are a natural part of the acceleration measurements and in many cases are allowed to be present to maintain the needed high-frequency responses. Crystal accelerometers are, for instance, essentially undamped, and have resonance humps 40 dB above unity in order to maintain a flat response to approximately one-half the resonance or natural frequency of the accelerometer. This resonance also allows the phase angle response to be close to zero well out towards the natural frequency. Additional resonance problems exist in the mounting brackets, or as frame resonances which carry little or no information. The process of removing them, however, can produce extreme errors in both amplitude and phase. The SAE J211a Recommended Practice recommends four channel classes for impact tests: c1asses 60, 180, 600, and 1000. The frequency response is flat to +1/2, -1 dB to these frequencies, and to +1, -4 dB to the break frequencies of 100, 300, 1000, and 1650 Hertz. The filter rolloff is nominally 12 dB/octave (second order) from these break points. Second order filters are normally used for impact tests since accelerometers have second order response. This filtering will provide satisfactory results, if no resonance is present at less than several times the class frequency. Often the next lower class is used to remove a resonance, a step that may cause large errors. A better solution is to follow the typical class filter with a sharper cutoff filter that will remove the resonance without affecting the amplitude and phase of the initial impulse. A method that determines when data is lost by excessive filtering is presented and demonstrated on two crashes. One crash has a resonance about 15 times higher than the class; one is less than 3 times higher.

The design and field-testing of a telemetry link to send signals to the surface of the earth from an earth penetrator are described. The link uses a PCM/FM format at a frequency of 10.5 kHz, dissipates 8 watts, and fits within a cylinder with an inside diameter of 100 mm. A bit error rate of less than 10⁻⁵ was achieved from a depth of 52 meters at a bit rate of 10³ bits per second.

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